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G Reuter

Publications and source records attributed to G Reuter.

At least 55 records · Page 3Linked to original sources
PubMed1997

Comparison between intact and desialylated human serum amyloid P component by laser photo CIDNP (chemically induced dynamic nuclear polarization) technique: an indication for a conformational impact of sialic acid.

The human pentraxin serum amyloid P component (SAP) exhibits no microheterogeneity in its complex di-antennary glycan. To elucidate whether the removal of sialic acids from this glycoprotein might affect the accessibility of certain amino acid residues of the protein we employed the laser photo CIDNP approach as a sensitive tool. The CIDNP effect is generated by the interaction of a photoexcited dye with reactive amino acids and results in enhanced absorption- or emission-signals which can be observed for the three aromatic amino acids histidine, tryptophan, and tyrosine if they are accessible to the dye. Therefore, this technique can be applied to explore surface exposure of these amino acid residues. The respective spectra of SAP and enzymatically desialylated SAP were determined. Six tryptophan/histidine signals and one tyrosine signal are present in the aromatic part of the CIDNP difference spectrum of SAP. The corresponding spectrum of desialylated SAP shows remarkable alterations. The chemical shift of one Trp/His-characteristic signal is decreased by 0.1 ppm. One Trp/His-signal disappeared and a new one was formed in the CIDNP difference spectrum of desialylated SAP, while the other signals were unaffected. The Tyr signal has a clearly enhanced intensity in desialylated SAP. Therefore, the removal of sialic acid moieties from the single N-glycan of each monomer apparently affects surface presentation of distinct CIDNP-reactive amino acids of SAP [1]. A conformational change of the protein part of SAP in relation with a different orientation of the desialylated oligosaccharide chain in comparison to the complete one is a possible explanation of our CIDNP results.

Carbohydrate Conformation↗
PubMed1997

Both invariant chain isoforms Ii31 and Ii41 promote class II antigen presentation.

The invariant chain (Ii) gene encodes two differentially spliced variants Ii31 and Ii41. The Ii31 isotype is the dominant form expressed in all antigen-presenting cells (APC). Ii41 is differentially expressed and can be found in large quantities in Langerhans and dendritic cells. While a functional role of Ii in class II antigen presentation is now well established, a distinct role of the Ii isotypes remains controversial. We tested Ii31 and Ii41 L cell transfectants for antigen presentation of hen egg lysozyme (HEL) to T cell hybridomas. The result indicates that both Ii chains promote antigen presentation equally well. To test other APC than transfected L cells, we introduced a recombinant Ii41 gene into anti-deficient mouse line. There the transgene induces about one-third of total li expression of wild-type mice. Surface expression of class II molecules and the CD4 compartment which are deficient in Ii knock-out mice are restored in Ii41 transgenic mice. B lymphocytes from Ii41 transgenic mice and Ii31-expressing B lymphocytes from wild-type mice were used as APC for presentation of keyhole limpet hemacyanin and ovalbumin to T cell hybridomas. The results show that both Ii chains facilitate antigen presentation equally well.

Animals↗
PubMed1997

Optical imaging of cat auditory cortex cochleotopic selectivity evoked by acute electrical stimulation of a multi-channel cochlear implant.

We measured reflectance changes by means of optical imaging of intrinsic signals to study the effects of acute electrical cochlear stimulation on the topography of the cat auditory cortex. After single-pulse electrical stimulation at selected sites of a multichannel implant device, we found topographically restricted response areas representing mainly the high-frequency range in AI. Systematic variation of the stimulation pairs and thus of the cochlear frequency sites revealed a systematic and corresponding shift of the response areas that matched the underlying frequency organization. Intensity functions were usually very steep. Increasingly higher stimulation currents evoked increasingly larger response areas, resulting in decreasing spatial, i.e. cochleotopic, selectivity; however, we observed only slight positional shifts of the focal zones of activity. Electrophysiological recordings of local field potential maps in the same individual animals revealed close correspondence of the locations of the cortical response areas. The results suggest that the method of optical imaging can be used to map response areas evoked by electrical cochlear stimulation, thereby maintaining a profound cochleotopic selectivity. Further experiments in chronically stimulated animals will shed more light on the degree of functional and reorganizational capacities of the primary cortex and could be beneficial for our understanding of the treatment of profound deafness.

Animals↗
PubMed1997

Quantitation and histochemical localization of galectin-1 and galectin-1-reactive glycoconjugates in fetal development of bovine organs.

The display of cellular oligosaccharide chains is known to undergo marked developmental changes, as monitored histochemically with plant lectins. In conjunction with endogenous lectins respective ligand structures may have a functional role during fetal development. The assumption of a recognitive, functionally productive interplay prompts the study of the expression of a tissue lectin and of lectin-reactive glycoconjugates concomitantly. Focusing on common beta-galactosides as constituents of oligosaccharide chains and the predominant member of the family of galectins in mammals, namely galectin-1, the question therefore is addressed as to whether expression of lectin and lectin-reactive glycoconjugates exhibits alterations, assessed in three morphologically defined fetal stages and in adult bovine organs. Using a sandwich ELISA, the level of the rather ubiquitous galectin-1 is mostly increased in adult organs relative to respective fetal stages, except for the case of kidney. This developmental course is seen rather seldom, when the amounts of lectin-reactive glycoproteins or glycolipids are quantitated in solid-phase assays after tissue homogenization. Western blotting, combined with probing by labeled galectin-1, discloses primarily quantitative changes in the reactivity of individual glycoproteins. Performing the same assays on extract aliquots with a plant agglutinin, namely the galactoside-binding mistletoe lectin, whose fine specificity is different from galectin-1, its reduced extent of binding in solid-phase assays and the disparate profile of lectin-reactive glycoproteins reveal a non-uniform developmental alteration within the group of structural variants of beta-galactosides. Although sample preparation can affect ligand preservation and/or presentation and thus restricts the comparability of biochemical and histochemical results, especially for soluble reactants, the histochemical studies on frozen and paraffin-embedded sections of bovine heart, kidney and liver demonstrate that the localization of the galectin and of lectin-reactive epitopes can show a similar distribution, as seen in liver and heart, with organ-typical quantitative changes of a rather similar staining profile (heart, kidney) or notable changes in the spatial distribution (liver) in the course of development. This report emphasizes the potential value of combined monitoring of the lectin and its potential in vivo ligands to contribute to eventually unravel organ-related function(s) of a tissue lectin.

Animals↗
PubMed1997

Intracochlear, electrical, multichannel stimulation effects on the development of auditory system in neonatally deafened kittens.

OBJECTIVE: To investigate the effect of chronic electrical stimulation in acoustically deprivated animals during maturation. MATERIALS AND METHODS: Latencies of EABR measurements from acoustically deprivated and acoustically deprivated, but electrically stimulated animals were compared with ABR from normal hearing cats. In addition, morphological analyses of the cochlear nuclei and the auditory cortex and their subdivisions were done. RESULTS AND DISCUSSION: EABR latencies demonstrated that the most peripheral auditory pathway is more independent from the normal auditory or external electrical stimulation than the more central regions. Morphological analysis also demonstrated the reverse of the acoustically deprivation effect during maturation in the auditory cortex via intracochlear electrical stimulation.

Animals↗
PubMed1997

Optical imaging of cat auditory cortical organization after electrical stimulation of a multichannel cochlear implant: differential effects of acute and chronic stimulation.

OBJECTIVE: To study the effects of electrical stimulation on cortical activation patterns. MATERIALS AND METHODS: Optical imaging of auditory cortex in cats that are acutely and chronically electrically stimulated with cochlear implants. RESULTS: Chronic electrical stimulation results in expansion of cortical territory and overlap. CONCLUSION: Effects of chronic electrical stimulation are comparable to use-dependent cortical plastic reorganization.

Animals↗
PubMed1997

Acute effects of electrical intracochlear multichannel high-rate stimulation of the auditory nerve of cats.

OBJECTIVE: To investigate the short-term effects of electrical stimulation of the cochlea in cats. MATERIALS AND METHODS: Deafened cats were implanted with human cochlear electrodes, electrical stimulation at clinical levels was given, and evoked auditory brain stem responses (EABR) were recorded. RESULTS AND DISCUSSION: No long-term reduction in the excitability of the auditory nerve or in brain stem responses was seen.

Animals↗
PubMed1997

Measurements of threshold shifts observed when using normal and preformed electrodes.

OBJECTIVE: To investigate the efficacy of short-term electrical stimulation with different human electrodes using high stimulation rates and different electrode designs. MATERIALS AND METHODS: Human electrodes of two different designs were implanted in cats, and electrically evoked auditory brain stem responses (EABR) were recorded. RESULTS AND DISCUSSION: Thresholds from the EABR recordings at the apical end of the electrode array were comparable in both types of implants. There were significantly higher thresholds at the basal end than at the apical end of the electrodes in both types of electrodes.

Acoustic Stimulation↗
PubMed1997

[Veterinary medicine and preventive medicine].

Veterinary medicine concentrates its main activities onto the curative practice for animals but also onto the field of health protection for men since a very long time. But as late as in the year 1900 the first regulation by law within the modern world was edited in Germany. It was initiated by the well-known pathologist Virchow in Berlin and elaborated, besides other veterinarians, by the first food hygienist at the Veterinary School of Berlin, Robert von Ostertag. At that time, the protection of men from the classical infections caused by bacteria was the target, e.g. tuberculosis and the so-called food poisoning. Also, parasitoses like trichinellosis or hydatidosis were the most fought enemies. Nearly 100 years after the application of this regulation by law new types of zoonoses or zooanthroponoses get importance in the view of preventive medicine fulfilled by veterinarians. That are infections which can not be recognized visually and clinically in the new breeding and fattening ways for animals. Such latent infections are the main targets in the present goals and objectives of food hygiene. An undefined and unsolved problem seems to be the occurrence of the BSE of cattle in Great Britain. It may be regarded as a new and intermediate form of a latent and apparent disease of animals which may be dangerous by an unknown way also for men. Since the seventies of this century, the interest of veterinary medicine was focussed also onto residue levels within the products from food animals. These are caused by "substances with pharmacological efficacy", illegally handled by agronoms or veterinarians or by "poisons from the contaminated environment" provoked by industrial emission or manipulations by men. A classical task of food hygiene within the veterinary medicine is to protect the consumer from being taken advantage of through the sale of products containing substantial disregulatory structures of animal tissues.

Animal Diseases↗
PubMed1996

The histone deacetylase RPD3 counteracts genomic silencing in Drosophila and yeast.

Both position-effect variegation (PEV) in Drosophila and telomeric position-effect in yeast (TPE) result from the mosaic inactivation of genes relocated next to a block of centromeric heterochromatin or next to telomeres. In many aspects, these phenomena are analogous to other epigenetic silencing mechanisms, such as the control of homeotic gene clusters, X-chromosome inactivation and imprinting in mammals, and mating-type control in yeast. Dominant mutations that suppress or enhance PEV are thought to encode either chromatin proteins or factors that directly affect chromatin structure. We have identified an insertional mutation in Drosophila that enhances PEV and reduces transcription of the gene in the eye-antenna imaginal disc. The gene corresponds to that encoding the transcriptional regulator RPD3 in yeast, and to a human histone deacetylase. In yeast, RRD3-deletion strains show enhanced TPE, suggesting a conserved role of the histone deacetylase RPD3 in counteracting genomic silencing. This function of RPD3, which is in contrast to the general correlation between histone acetylation and increased transcription, might be due to a specialized chromatin structure at silenced loci.

Amino Acid Sequence↗
PubMed1996

Binding specificity of influenza C-virus to variably O-acetylated glycoconjugates and its use for histochemical detection of N-acetyl-9-O-acetylneuraminic acid in mammalian tissues.

The specificity of influenza C-virus binding to sialoglycoconjugates was tested with various naturally O-acetylated gangliosides or synthetically O-acetylated sialic acid thioketosides, which revealed binding to 9-O-acetylated N-acetylneuraminic acid. Binding was also observed with a sample of Neu5,7Ac2-GD3, however at a lower degree. Sialic acids with two or three O-acetyl groups in the side chain of synthetic sialic acid derivatives are not recognized by the virus. In these experiments, bound viruses were detected with esterase substrates. Influenza C-virus was also used for the histological identification of mono-O-acetylated sialic acids in combination with an immunological visualization of the virus bound to thin-sections. The occurrence of these sialic acids was demonstrated in bovine submandibular gland, rat liver, human normal adult and fetal colon and diseased colon, as well as in human sweat gland. Submandibular gland and colon also contain significant amounts of glycoconjugates with two or three acetyl esters in the sialic acid side chain, demonstrating the value of the virus in discriminating between mono- and higher O-acetylation at the same site. The patterns of staining showed differences between healthy persons and patients with colon carcinoma, ulcerative colitis or Crohn's disease. Remarkably, some human colon samples did not show O-acetyl sialic acid-specific staining. The histochemical observations were controlled by chemical analysis of tissue sialic acids.

Acetylation↗
PubMed1996

Molecular dynamics-derived conformation and intramolecular interaction analysis of the N-acetyl-9-O-acetylneuraminic acid-containing ganglioside GD1a and NMR-based analysis of its binding to a human polyclonal immunoglobulin G fraction with selectivity for O-acetylated sialic acids.

The influence of 9-O-acetylation of GD1a, yielding GD1a (eNeu5,9Ac2) with a 9-O-acetylated sialic acid moiety linked to the outer galactose residue, on the spatial extension and mobility of the carbohydrate chain and on recognition by a natural human antibody is analysed. To study a potential impact of the O-acetyl group on the overall conformation of the carbohydrate chain, molecular dynamics (MD) simulations of oligosaccharide chain fragments of increasing length starting from the non-reducing end have been carried out for the first time in this study. They revealed a considerable loss in chain flexibility after addition of the internal N-acetylneuraminic acid onto the chain. Besides MD calculations with different dielectric constants, the conformational behaviour of the complete oligosaccharide chain of the 9-O-acetylated GD1a ganglioside was simulated in the solvents water and dimethyl sulfoxide. These solvents were also used in NMR measurements. The results of this study indicate that 9-O-acetylation at the terminal sialic acid does not influence the overall conformation of the ganglioside. An extended interaction analysis of energetically minimized conformations of GD1a (eNeu5,9Ac2) and GD1a, obtained during molecular dynamics simulations, allowed assessment of the influence of the different parts of the saccharide chains on spatial flexibility. Noteworthy energetic interactions, most interestingly between the 9-O-acetyl group and the pyranose ring of N-acetylgalactosamine, were ascertained by the calculations. However, the strength of this interaction does not force the ganglioside into a conformation, where the 9-O-acetyl group is no longer accessible. Binding of GD1a (eNeu5,9Ac2) to proteins, which are specific for 9-O-acetylated sialic acids, should thus at least partially be mediated by the presence of this group. To experimentally prove this assumption, a NMR study of 9-O-acetylated GD1a in the presence of an affinity-purified polyclonal IgG fraction from human serum with preferential binding to 9-O-acetylated sialic acid was performed. The almost complete disappearance of the intensity of the 9-O-acetyl methyl signal of the GD1a (eNeu5,9Ac2) clearly indicates that the assumed interaction of the 9-O-acetyl group with the human protein takes place.

Acetylation↗
PubMed1996

Lactobacillus curvatus subsp. curvatus subsp. nov. and Lactobacillus curvatus subsp. melibiosus subsp. nov. and Lactobacillus sake subsp. sake subsp. nov. and Lactobacillus sake subsp. carnosus subsp. nov., new subspecies of Lactobacillus curvatus Abo-Elnaga and Kandler 1965 and Lactobacillus sake Katagiri, Kitahara, and Fukami 1934 (Klein et al. 1996, emended descriptions), respectively.

Lactobacillus curvatus and Lactobacillus sake are each genetically homogeneous species, as indicated by the high levels of DNA homology (> or = 76%) exhibited by strains of these taxa. However, the results of a numerical analysis of total soluble cell protein patterns and biochemical test data revealed that there are two phenotypic subgroups within L, curvatus and two phenotypic subgroups within L. sake. The overall randomly amplified polymorphic DNA (RAPD)-PCR band patterns obtained for the majority of L. curvatus strains corresponded well to the pattern obtained for the type strain of L. curvatus (strain DSM 20019). However, six strains of L. curvatus had different, but similar, RAPD-PCR profiles and grouped in a separate genetic cluster, which was linked to one of the clusters of L. sake strains. On the basis of these results, differences in biochemical and physiological characteristics, and total soluble cell protein profiles, we describe the subspecies L. curvatus subsp. curvatus subsp. nov. and L. curvatus subsp. melibiosus subsp. nov. for L. curvatus Abo-Elnaga and Kandler 1965 (Klein et al. 1996, emended description). Strains of L. sake grouped in two RAPD-PCR clusters, which was consistent with previous reports of phenotypic heterogeneity. Strains of Lactobacillus bavaricus, including type strain LMG 9844, clustered with the type strain of L. sake (strain NCFB 2714), indicating that these organisms belong to the same genetic group. We propose that strains of L. sake Katagiri, Kitahara, and Fukami 1934 (Klein et al. 1996, emended description) should be reclassified as members of L. sake subsp. sake subsp. nov. and L. sake subsp. carnosus subsp. nov. Strains of L. bavaricus are reclassified as members of L. sake subsp. sake, and the name L. bavaricus Stetter and Stetter 1980 is rejected.

DNA, Bacterial↗
PubMed1996

Position-effect variegation in Drosophila depends on dose of the gene encoding the E2F transcriptional activator and cell cycle regulator.

A dominant mutation due to the insertion of a P-element at 93E on the third chromosome of Drosophila melanogaster enhances position-effect variegation. The corresponding gene was cloned by transposon tagging and the sequence of the transcript revealed that it corresponds to the gene encoding the transcriptional activator and cell cycle regulator dE2F. The transposon-tagged allele is homozygous viable, and the insertion of the transposon in an intron correlates with a strong reduction in the amount of transcript. A homozygous lethal null allele was found to behave as a strong enhancer when heterozygous. Overexpression of the gene in transgenic flies has the opposite effect of suppressing variegation. A link is established here, and discussed, between the dose of a transcriptional activator, which controls the cell cycle, and epigenetic silencing of chromosomal domains in Drosophila.

Amino Acid Sequence↗
PubMed1996

Sialic acids structure-analysis-metabolism-occurrence-recognition.

Sialic acids are commonly positioned at non-reducing termini of complex carbohydrates. Steady refinements of analytical techniques have enabled detailed mapping of the complexity of sialic acids, unravelling a number of possibilities for substitutions. These developments have aided the description of the required enzymatic activities. In view of the physiological significance of this intriguing extent of variability of one sugar unit, the assumption that distinct types of sialic acids can serve as ligands in recognitive interactions is gaining support. It is reinforced by the discovery of several classes of mammalian lectins that bind sialo-glycoconjugates. Notably, an often encountered modification of sialic acids, namely O-acetylation, can be considered as a modulatory signal in recognition, either serving as contact point or masking a ligand structure. The increased knowledge of the physiological roles of sialic acids, for example in selectin-mediated leukocyte recruitment to sites of inflammation or in influenza virus propagation, even points to clinical applications. This perspective has led the field from the inherently descriptive beginning to technically sophisticated attempts for deliberate drug design.

Animals↗
PubMed1995

Effect of enzymatic desialylation of human serum amyloid P component on surface exposure of laser photo CIDNP (chemically induced dynamic nuclear polarization)--reactive histidine, tryptophan and tyrosine residues.

The human pentraxin serum amyloid P component (SAP) exhibits no microheterogeneity in its complex di-antennary glycan. To elucidate whether the removal of sialic acids from this glycoprotein might affect the accessibility of certain amino acid residues of the protein we employed the laser photo CIDNP approach as a sensitive tool. The CIDNP effect is created by the interaction of a photoexcited dye with reactive amino acids and results in enhanced absorption- or emission-signals which can be observed for the three aromatic amino acids histidine, tryptophan, and tyrosine if they are accessible to the dye. Therefore, this technique can be applied to explore surface exposure of these residues. The respective spectra of SAP and enzymatically desialylated SAP were determined. Six tryptophan/histidine signals and one tyrosine signal are present in the aromatic part of the CIDNP difference spectrum of SAP. The corresponding spectrum of desialylated SAP shows remarkable alterations. The chemical shift of one tryptophan/histidine-characteristic signal is decreased by 0.1 ppm. One tryptophan/histidine signal disappeared and a new one was formed in the CIDNP difference spectrum of desialylated SAP, while the other signals were unaffected. The tyrosine signal has a clearly enhanced intensity in desialylated SAP. Therefore, the removal of sialic acid moieties from the single N-glycan of each monomer apparently affects surface presentation of distinct CIDNP-reactive amino acids of SAP.

Amino Acids↗